1. FIELD OF THE INVENTION
The invention relates to the field of magnetic recording heads, especially, vertical recording heads.
2. BRIEF DESCRIPTION OF THE PRIOR ART
Recently developed, single-sided, vertical recording, probe heads have a narrow, Permalloy, trailing probe pole and a broad ferrite flux return path spaced some distance away from the probe pole so that the trailing edge magnetic field orientation is concentrated and vertical. A typical arrangement is shown in FIG. 1 (PRIOR ART).
In this figure, head 10 flies on an air bearing a short distance above media 20. The head has a trailing probe pole 14 composed of a highly magnetically permeable material such as found in the Permalloy family. The probe pole 14 is mounted on a ferrite substrate 12, which also forms the part of the flux path. At the air bearing surface 30 facing the media 20, a wide gap 22 is formed between the probe pole 14 and ferrite 12. This is conventionally filled with a non magnetic filler such as glass. Coils 16 are mounted in a gap 24, conventionally filled with non magnetic photoresist. The coils provide magnetic flux for writing and sense magnetic flux for reading. The flux path is closed by magnetically permeable underlayer 32.
A problem in this design is that it is inefficient for reading. The probe tip 18 is made relatively thick to avoid saturation and to provide a high magnetic field gradient for narrow magnetization transitions and acceptable overwrite. However, on readback, it is desirable to have a thin, narrow tip to increase resolution for acceptable high density performance.
U.S. Pat. No. 4,639,811 discloses a two-pole, single-gap, two-coil, vertical-recording, read-ring head, one pole of which saturates on writing. No write flux return path is provided, which makes the head inefficient for writing and undoubtedly accounts for the separate write coil.